fix: RM additional menu popup bg

[zombieJ]

🤔 This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

🔗 Related issue link

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English	Remove useless popup Menu cover background color.
🇨🇳 Chinese

☑️ Self Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

[ant-design-bot]

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[codecov]

Codecov Report

Merging #21365 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #21365   +/-   ##
=======================================
  Coverage   97.55%   97.55%           
=======================================
  Files         300      300           
  Lines        7003     7003           
  Branches     1884     1884           
=======================================
  Hits         6832     6832           
  Misses        171      171

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[afc163]

changelog 写的不好，没有主语。

[afc163]

https://github.com/ant-design/ant-design/pull/21396/files#r379904983